Diplex antenna feed system



Jan. 29, 1952 M. E. HIEHLE 2,583,773

DIPLEX ANTENNA FEED SYSTEM I Filed July 30, 194B Inverwtor; Mitzh'ael B. Hiehle,

H is Attorrwey referretl to as diplexers.

Patented Jan. 29, 1952 UNITED STATES PATENT OFFICE DIPLE X ANTENNA FEED SYSTEM Michael E. Hiehle,'Syracuse, N. Y., assignor to General Electric Gompany,

New York a corporation of Application July 30, 1948, SefiaI'NO. 41,628

The diplexers embodying this invention operate on the principle ofsimultaneously feeding energy from two transmitters to a common load through anintermedi'ate circuit. Briefly, energy from one transmitter is fed, in a push-pull relationship, to two utilization points, While that from theother transmitter is fed, in a parallel relationship, through the midpoint or a half wavelength loop connecting the utilization points. By proper selection of the characteristic impedances of the sections, both transmitters may feed into the same. load and yet remain completely decoupled. These principles are well known in the art and will not he described indetail. My invention resides in certain improved constructional features of the diplexer assembly, and more particularly in "the utilization of the outside sheaths ofsingle coaxial transmission lines to perform functions separatefrom thoseof the inside conductors.

Oneiof 'the objects of the present inven'tion'is toiprovidea new and-improved diplexer to enable twortransmitterS, operating at different. frequencies, tofeed'simultaneously to the same antenna, in such a manner that there is no reaction between the transmitters over a wide range of fre- 'quencies.

A further object of this invention is to provide a'new and improved diplexer for guiding energy from a pair of'transmitters to apair of antennae through single concentric transmission lines in such a manner that there is no reaction between For additional objects and advantages andrfor a better understanding of the invention, attention 'i-snow directed to the following description and accompanying drawing, and also to the'appended claims in which the features of. the invention believedito be novel are particularly pointed out.

in the drawing, Fig. l 'is a perspective view of adiplexer embodying my invention, with part of its container cut away to facilitate understanding of itsinternal arrangement, Fig. 21similarly shows another diplexer embodying my in-.- vention in modified form, and Fig. 3 :shows a modification of the diplexer of Fig.1.

In bo'th Fig. 1 and Fig. 2, the symbol refers to a quarter wavelength at'the operating frequency of the visual transmitter, while the symbol branches at a.point 3l from whence. two concentric lines .3f3 ,and 34 feed energy into the system- The transmission-lineliis adaptedto be energized from aneural televisionttransmitter at. the aural input point 4.. .They parallel branches are terminated at theright end wall of. a. conductive container 10, and the branches and .34 are of such length thattogether they .form

a loop one-half wavelength long at. the mean operating frequency of. the visual transmitter. Whilethe container l'll'has been shown as rectangular inform,. it is to be understood that it can be of any convenientform, such as a tubular cantor instance.

Two concentric transmission lines 24' and'lli withinner conductor 23 and 2"5"also terminate in the right' end wall ofthe container. 'There are adapted to supply energy at output terminals I an'd'ito a-"pairbfaritennae. For the-purpose of obtaining a phase I quadrature relationship in the cutputof one'antenna'with respect to the "output of the-othenaloop 21 is introducedin the concentric line 26. "This"loopisa quarter oi 'a wavelength long-attire mean-operating frequency of the system, taking into account the frequencies of hoth' the "visual and aural transmitters.

The linesections H and: It: within: container I'D are: arranged to provide: two intermediate :points 1 and 8 f fromwhich energy. from the visual transjvoltage relations at these points.

sheath I3 at the left end wall of the container, it I is curved at this wall to join the outer sheath I I, and its left section is actually a concentric line containing .an inner conductor I4 which is connected to the visual input line at a point I6. A shorting plug I5 provides a conductive connection between the inner conductor I4 and the sheath I 3. The section of transmission line from point I8 to the shorting plug, considered solely as a concentric line and without reference to the function of the outer sheath in the container,

providesa matching stub removed approximately one-quarter wavelength from the termination I ofthe visual input line. This matching stub is employed for the purpose of broadening the band passof the system about the visual input frequency so as to permit operation over a two to one frequency jrange. The container I0, surrounding sheath II, isolates it from ground at the operating frequency so that the voltage between the inner conductor I2 and sheath II is approximately balanced to ground at the intermediate point 1. The inner conductor I2 of the .visual input lineis connected by a short conductive link 2| to sheath I3 at point 8. The energy is thereby transferred into the field existing between sheaths II and I3. These sheaths II and I3 together constitute a two-wire transmission line. A shorting bar 22, for which a capacitance may be substituted incertain cases, is mounted so that it can he slid over the sheaths II and I3 so as-to adjust their electrical length. The sliding 'bar is normally adjusted so that the quarter wave stub constituted by sheaths I I and I3 constitutes a very high impedance at the visual input frequency, as seen from points I and 8. Two pairs of capacitor plates and 36, mounted at the free 'ends of sheaths I I and I3, provide additional flumped capacity to broaden the aural frequency bandwidth of the system and to insure electrical Since the Accordir'ig'ly, if the terminals are connected to two points carrying out-of-phase voltages, such as points I and 8, there will be no disturbance of the Moreover. such voltages applied at the input terminals arrive at the junction point 3| in an out-of-phase relationship so that no visual current can flow past the junction point to the aural transmitter. The end result will be that, the aural transmitter .is coupled to supply parallel voltages to points 1 and 8 and yet remains completely decoupled from the visual transmitter.

The sheaths II and I3, while they have already been considered as a pair of linear conductors constituting a quarter wavelength stub inside container I flycan also be considered as forming, in parallel, a single inner conductor inside container ]8. When the sheaths I I and I3 are excited in parallel, an electric field will exist between them and container I0. The length of the conducting path is close enough to a quarter wavelength at the operating frequency of the aural transmitter so as to ofler a comparatively high impedance between points I and 8 in parallel, to the boundary of the container. Accordingly the voltage from the aural input line exists between points I and 8 in parallel and the container boundary. This voltage cannot affect the visual transmitter, because the same voltage exists on point I as on point 8 and hence there can be no difierence of potential between point I and the inner conductor I2 of the visual input line at the aural frequency. The

container as an outer conductor. .bar. 22, enables the diplexer to be quickly ad- ;justed to operate effectively at any frequency ,within a two-to-one range of frequencies, and

result of the arrangement is that the visual transmitter supplies voltages to points I and 8 in a push-pull relationship and yet remains completely decoupled from the aural transmitter. A pair of short connectors I1 and I8 couple the voltages existing at points, I and 8 to the inner conductors 23 and 25 of the antenna output lines. The antenna output lines are thus supplied with voltages in a push-pull relationship from the visual transmitter and in a parallel relationship from the aural transmitter. An external quarter wavelengthloop in theconcentric line 26 provides a phase retardation of in that line so that the voltages arrive at the antennae in phase quadrature.

, The arrangement of Fig. 1, as thus far described, has the advantage of utilizing single concentric lines to perform all the functions required in the diplexer. tainer perform multiple functions: as a concentric matching stub, considering the inner section of line I3 from point I6 to shorting plug I5; as atwo-wire transmission line, considering sheaths I I and I3 as a pair of linear conductors; and

as a high impedance considering sheaths II and I3 as elements in parallel with respect to the The sliding thus only one adjustment is required to tune the system. This arrangement has been found In practice 00- sheath 58 and an inner conductor 5| which is adapted, to receive energy from a visual tele vision transmitter at an input point 43. A similar concentric line 66 is shown divided into two parallel branches 68 and 69, at a point 61, from whence the two parallel branches feed energy into the system. The transmission .line 56 is adapted to be energized from an aural television transmitter at input point 40'. The parallel branches are terminated at the right end wall'of a rectangular conductive container 45, and "they are of such length, that together they .form a loop one-half wavelength long at the mean.operating frequency of the visual transmitter. Two concentric lines 46 and 48 enter the container through the left" end wall and .terminate at points 11 and 18 at a distance from the left end wall, of approximately one-quarter of a wavelength at the operating frequency of the visual transmitter. The inner conductors 41 The lines inside the con single concentric lines.

manner as in the diplexer of Fig. 2. particularly useful for operation at higher freatesyrve and. 49 continuedirectly to the right end wall of the container 45, and are there conductively connected to it. The sheaths 46 and 48 are, everywhere along their length, in contact, respectively, with the sheath 5!! of the visual input line and a dummy sheath 52, symmetrically located with respect to sheath 5i! inside the container. As in the diplexer of Fig. l, the outer sheathiil and dummy sheath 52 form elements of an openwire transmission line section, shorted at its left end-by means of adjustable shorting straps 51.

As in the case of the embodiment shown in Fig. 1, the pairs of sheaths are excited inpushpull from the visual input and in parallel from the aural input. This diplexer is intended to operate at a higher frequency than that of Fig. l and it has been found expedient to neutralize the inductance inherently present in the connecting link 55, by means of a series capacitance. This inductance is shown in dotted outline in Fig. 2. The neutralization is effected by running an inner conductor 53 into the dummy sheath 52. The short length of inner conductor 53 into sheath 52 can be considered as an open-ended transmission line and accordingly provides a capacitance whose value can be altered by adenergy. To compensate for this effect a small coil is connected between link 56 and the right end wall of the container and is chosen *to provide parallel resonance in conjunction with the stray capacity.

Since the inner conductors of the antenna output lines are connected directly to the right wall of the grounded container, the voltages existing on the outer sheaths at points 11 and 18 are transferred to the inner conductor through the length of the quarter wave section going to the left wall of the tube. Thence the output voltages are transmitted to the antenna through regular A quarter wave loop 65 is introduced in one of the lines to provide a quadrature relationship in the voltages at the antenna.

The construction shown in the embodiment of Fig. 2 also has the advantage of using ordinary "concentric lines to perform all the necessary functions. The inversion of the feed to the antenna by the grounding of the inner conductors inside the tube has the advantage of more easily achieving the low impedance match required.

Fig. 3 shows a modification of the diplexer of Fig. 1 in which the inherent inductance of the connecting link 2! is neutralized in the same This is tion of this modification are the same as for the diplexer of Fig. 1.

While certain specific embodiments have been shown and described, it will, of course, be understood that various modifications may be made without departing from the invention. The appended claims are therefore intended to cover :any such modifications within the true spiritand scope of the invention.

What Iclaim as new and desire to secure b Letters Patent of the United States is:

1. Adiplexer structure for supplying electrical wave energy to a common pair of load circuits from two separate high-frequency transmitters, comprising a closed conductive container, a concentric transmission line having an inner conductor and an outer sheath energized from a first one of said transmitters, said line having an end portion penetrating a wall ofsaid container approximately an odd multiple of a quarter-wavelength at the operating frequency of said first transmitter, said outer sheath being connected to said wall of said container at its point of entrance and having a free end within said container constituting a first feed point, a linear-conductor in said container substantially parallel to said portion, said linear conductor having one end connected to said wall adjacent said point of entrance and having a free end forming a second feed point adjacent said first feed point, said outer sheath and linear conductor together forming an open-wire transmission line section, means comprising an adjustable shorting member bridging said section for independently adjusting the efiective length of said section atthe operating frequency of said first transmitter, circuit connections for supplying wave energy from said inner conductor to said second feed point, said feed points being energized in opposite phase from said first transmitter, means for energizing said feed points in the same phase from said second transmitter, said means comprising a pair of unbalanced transmission line sections energized in parallel, said line sections each having a length substantially equal to an odd number of quarter-wavelengths at the operating frequency of said first transmitter, and a pair of transmission lines energized from said respective feed points for supplying energy from said points to said pair of load circuits.

2. A diplexer structure for supplying electrical wave energy to a common pair of load circuits from two separate high-frequency transmitters, comprising a closed conductive container, a concentric transmission line having an inner conductor and an outer sheath energized from a first one of said transmitters, said line having an end portion penetrating a wall of said container approximately an odd multipleoi a quarter-wavelengthat the operating frequency of said first transmitter, said outer sheath being connected to said Wall of said container at its point of entrance and having a free end within said container constituting a first feed point, a conductive tube in said container, said tube having an unsupported section extending substantially parallel to said portion and a bent end section conductively connected to said sheath near said point'of entrance soas to form a branch sheath, an inner wire within said tube joined at one end to the inner conductor of said line and at the other end to an adjustable short-circuiting member' Within said tube, whereby said tubeencloses a concentric impedance-matching stub for said line, a low impedance connection between the free end of said straight section and saidinner conductor, means for adjusting the length of the two-wire transmission line formed by said line portion and said straight section to provide a second feed point at the free end of and section energized in phase opposition to said first feed point, means for energizing said feed points in the same phase from said second transmitter,

and a pair of transmission lines energized from said respective feed points for supplying energy from said points to said pair of load circuits.

3. A diplexer structure for supplying electrical wave energy to a common pair of load circuits from two separate high-frequency transmitters, comprising a closed conductive container, a concentric transmission line'having an inner conductor and an outer sheath energized from a first one of said transmitters, said line having an end portion penetrating a wall of said container approximately an odd multiple of a quarter-wavelength at the operating frequency of said first transmitter, said outer sheath being connected to said wall of said container at its point of entrance and having a free end within'said container constituting a first feed point, a conductive tube positioned in said container substantially parallel to said portion, said tube being conductively supported only at one end at said wall adjacent said point of entrance and providing a second feed point at its free end adjacent said first feed point, a linear conductor positioned within the free end of said tube and having a direct connection to said inner conductor, said linear conductor penetrating said tube a sufficient distance to provide a capacity reactance substantially resonating with series inductive reactance inherent in said direct connection, said outer sheath and tube together forming an open wire transmission line section, means comprising a shorting member bridging said section for independently determining the effective length of said section at the operating frequency of said first transmitter, said feed points being energized in opposite phase from said first transmitter, means for energizing said feed points in the same phase from said second transmitter, and a pair of concentric cables energized from said respective feed points for supplying energy from said points to said pair of load circuits.

4. A diplexer structure for supplying electrical wave energy to a common pair of load circuits from two separate high-frequency transmitters, comprising a closed conductive container, a'concentric transmission line having an inner conductor and an outer sheath energized from a first one of said transmitters, said line having an end portion penetrating a wall of said container approximately an odd multiple of a quarter-wavelength at the operating frequency of said first transmitter, said outer sheath being connected to said wall of said container at its pointof entrance and having a free end within said container constituting a first feed point, a conductive tube positioned in said container substantially parallel to said portion, said tube being conductively supported only at one end at said wall adjacent said point of entrance and providing a second feed point at its free end adjacent said first feed point, a linear conductor positioned within the free end of said tube and having a direct connection to said inner conductor, said linear conductor penetrating said tube a sufiicient distance to provide a capacity reactance substantially resonating with series inductive reactance inherent in said direct connection, said outer sheath and tube together forming an open wire transmission line section, means comprising a shorting member bridging said section for independently determining the effective length of said section at the operating frequency of said first transmitter, an inductance connected between said direct connection and the wall of said container, adjacent said feed points, to provide parallel resonance with prising an outer conductor and an inner wire,-

the outer conductor of one of said cables being in contact with said outer sheath along its length and the outer conductor of the other of said cables being in contact with said tube along its length, and said inner wires being conductively connected to a wall of said container adjacent said feed points.

5. A diplexer structure for supplying electrical wave energy to a common pair of load circuits from two separate high-frequency transmitters, comprising a closed conductive container, a concentric transmission line having an inner conductor and an outer sheath energized from a first one of said transmitters, said line having an end portion penetrating a wall of said container approximately an odd multiple of a quarter-wavelength at the operating frequency of said first transmitter, said outer sheathbeing connected to said wall of said container at its point of entrance and having a free end within said container constituting a first feed point, a conductive tube in said container, said tube having a straight unsupported section extending substantially parallel to said portion and a bent end section conductively connected to said sheath near said point of entrance so as to form a branch sheath, said outer sheath and said tube together forming an open wire transmission line section means comprising a shortthe free end of said tube and having a directconnection to said inner conductor, said linear conductor penetrating said tube a sufiicient distance to provide a capacity reactance substantially resonating with series inductive reactance inherent in 'said direct connection, said feed points being energizediin opposite phase from said first transmitter, means for energizing said feed pointsin the same phase from said second transmitter, and a pair of concentric cables energized from said respective feed points for supplying energy from said points to said pair of load circuits.

6. A diplexer structure for supplying electrical wave energy to a common pair of load circuits from two separate high-frequency transmitters, comprising a closed conductive container, a concentric transmission line having an inner conductor and an outer sheath energized from a first one of said transmitters, said line having an end portion penetrating a wall of said container approximately an odd multiple of a quarter-wavelength at the operating frequency of .said first transmitter, said outer sheath being connected to said wall of said container at its point of entrance and having a free end within said container constituting a first feed point,

quency, said outer sheath and linear conductor together forming an open-Wire transmission line section, means comprising a shorting member bridging said section for independently determining the effective length of said section at the operating frequency of said first transmitter, said feed points being energized in opposite phase from said first transmitter, means for energizing said feed points in the same phase from said second transmitter. said means comprising a pair of unbalanced transmission line sections energized in parallel, said line sections each having a length substantially equal to an odd number of quarter-wavelengths at the operating frequency of said first transmitter, and a pair of transmission lines energized from said respective feed points for supplying energy from said points to said pair of load circuits.

7. A diplexer structure for supplying electrical wave energy to a common pair of load circuits from two separate high-frequency transmitters, comprising a closed conductive container, a concentric transmission line having an inner conductor and an outer sheath energized from a first one of said transmitters, said line having an end portion penetrating a Wall of said container approximately an odd multiple of a quarter-wavelength at the operating frequency of said first transmitter, said outer sheath being connected to said wall of said container at its point of entrance and having a free end within said container constituting a first feed point, a

linear conductor positioned in said container substantially parallel to said sheath, said linear conductor being electrically connected to said container near said point of entrance and having a free end forming a second feed point adjacent said first feed point, means electrically con necting the inner end of said inner conductor the free end of said linear conductor to maintain them at the same potential at said frequency, said outer sheath and linear conductor together forming an open wire transmission line section. means comprising a shorting member bridging said section for independently determining the effective length of said section at the operating frequency of said first transmitter, said feed points being energized in opposite phase from said first transmitter, means for energizing said feed points in the same phase from said second transmitter, and a pair of transmission lines energized from said respective feed points for supplying energy from said points to said pair of load circuits.

MICHAEL E. HIEHLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 5 Number Name Date 2,318,237 Lindenblad May 4, 1943 2,473,328 Brown June 14, 1949 2,495,589 Masters Jan, 24, 1950 OTHER REFERENCES A Wide Band Transformer From an Unbalanced to a Balanced Line, by Fubini and Sutro. Reprinted from the Proceedings of the Institute of Radio Engineers, vol. 35, No. 10, October 1947, pages 11534155. 

